System for acquiring ultrasound images of internal body organs

ABSTRACT

A system for acquiring ultrasound images of internal body organs comprises a scanner and at least one inertial measurement unit (IMU) associated therewith, wherein the system is configured to issue instructions to the operator of the system that allow scans to be performed also by persons not trained for ultrasound scanning including the patient themselves, and wherein when the scans are performed by untrained operators, the scans are transmitted to a remote location for analysis by a healthcare professional.

FIELD OF THE INVENTION

The invention is from the field of medical devices. Specifically, theinvention relates to a system and method for accurately positioning andmoving a hand-held ultrasound probe utilizing an inertial measurementunit.

BACKGROUND OF THE INVENTION

Knowing the location of a medical sensor or a medical device relative toa patient's anatomical structure and the speed with which the sensor ordevice is or should be moving is critical for the functionality ofadvanced remote control, robotic, autonomous, self-feedback, or otherautomatic medical procedures.

The speed at which an ultrasound probe (also referred to hereinvariously as “scanner,” “ultrasound head,” or simply “probe” forsimplicity) moves across the body provides important information. Forexample, images taken at speed lower or higher than some range may bedeleted or possibly be subject to special filtering and image processingtechniques in order to enhance blurred images. Also, instruction may beprovided to the operator concerning several aspects of the proceduresuch as when to stop movements, how to correct the scan path, how tochange orientation or to tilt the probe, etc. In the case of remotecontrol of an ultrasound probe or a sensor mounted on a gimbal locatedon a patient's body, knowing the two-dimensional or three-dimensionalspeed at which the ultrasound probe moves is also important to track theoverall location, attitude and speed of the gimbal and/or the probe.

An extremely common procedure is ultrasound scanning, which inter alianearly every woman undergoes during prenatal visits to her doctor or aclinic. Typically, in this scenario, an ultrasound technician(sonographer) or physician performs the scans. The operator, i.e.technician, midwife, doctor, sonographer, etc. knows, based on theirexperience, the best position and orientation in which the scanner heador probe must be located in order to image specific structures of theembryo, the right amount of pressure against the belly that is necessaryto keep good coupling of the scanner to the body, the angle of the proberelatively to the belly, and the right scanning speed that will allowgood imaging. Moreover, the operator sees the images generated by theprobe on a screen in real time and is able to optimize or correct itsposition. Herein the term “probe” or “ultrasound probe” refers to anyuseful probe, linear or convex, phase array, HIFU, or other sensor.

In the context of this description the term “scanner,” should beunderstood to refer to an element, housing or device, which must moveover the surface of a patient's body to acquire data therefrom, e.g.,ultrasound images.

Many scans take place just to monitor the embryo's vitality signs, e.g.heartbeat, movement, amniotic fluid volume, tone, and respiration. Thesescans could also be executed by the patient at her home or otherlocation that is not a clinic, hospital or medical facility, thus savingthe overloaded medical system time and resources, and potentiallyavoiding an unnecessary visit to an emergency department or a prenatalvisit to the doctor's office, a clinic or a hospital. However,performing an ultrasound scan requires some of the ultrasound operator'sskill that untrained persons lack. It is clear that it would be highlydesirable to provide means by which an unskilled person can perform a“do-it-yourself” ultrasound scan that yields useful results.

It is therefore a purpose of the present invention to provide a deviceand method that assist a patient in performing an ultrasound scan bymonitoring the motion of the scanner head (ultrasound probe) andproviding feedback that assists in positioning the scanner head at thedesired location.

Further purposes and advantages of this invention will appear as thedescription proceeds.

SUMMARY OF THE INVENTION

In one aspect the invention relates to a system for acquiring ultrasoundimages of internal body organs, comprising a scanner and at least oneinertial measurement unit (IMU) associated therewith, wherein the systemis configured to issue instructions to the operator of the system thatallow scans to be performed also by persons not trained for ultrasoundscanning including the patient themselves, and wherein when the scansare performed by untrained operators, the scans are transmitted to aremote location for analysis by a healthcare professional.

In some embodiments, the system comprises an IMU-independent componentadapted to alert the user in case of insufficient coupling between theapparatus and the body. In other embodiments the system comprises anIMU-independent component adapted to alert the user if the scanningspeed it too fast.

In another aspect the invention encompasses a system for acquiringultrasound images of internal body organs. The system comprises ascanner and at least one inertial measurement unit (IMU) associatedtherewith.

In some embodiments of the system the at least one IMU is one of: a)integral with the scanner; b) connected to the scanner via a plug-inconnection; and c) provided in an element associated with the scannerand moving therewith during operation.

Some embodiments of the system are configured to issue instructions tothe operator of the system that allow scans to be performed also bypersons not trained for ultrasound scanning including the patientthemselves.

In some embodiments of the system wherein the scans are performed byuntrained operators, the scans are transmitted to a remote location foranalysis by a healthcare professional.

Some embodiments of the system are configured to allow two-waycommunication between the operator and a remote individual ornon-monitored system, wherein the non-monitored system comprisesautomated, image analysis circuitry. The term “monitored,” as usedherein, means that human supervision exists in the system. Contrarily,“non-monitored” systems are fully automated and do not involve humansupervision. The two-way communication can be selected from audio,visual, and video communication, and combinations thereof. In someembodiments of the system, when the scans are performed by untrainedoperators, two way video communication is enabled between the operatorand the health care professional, enabling them to see each other whilethe operator is carrying out the scanning procedure to aid the healthcare professional in interpreting the images and to provide guidance ifnecessary. In some embodiments the system is configured such that theoutput of the system is sent directly to a remote healthcareprofessional and/or to a non-monitored system either in real time orshortly after the images are acquired.

Some embodiments of the system are configured to overlay an image of thescanner on top of the ultrasound scans to aid a healthcare professionalin interpreting the images.

Embodiments of the scanner of the system comprise a housing that isergonomically designed to be held by an operator and moved across theskin of a person or animal. Some embodiments of the housing comprise, orhas associated therewith, at least the minimum number of components ofthe system that must be located on the patient's body to obtain theultrasound images. In some embodiments of the housing the minimum numberof components in, or associated with the housing are: i) an ultrasoundprobe head; ii) the at least one IMU, which comprises a three-axisaccelerometer and a three-axis gyroscope; iii) electronic components forwired or wireless communication with remote terminals, and iv) a powersource.

In some embodiments of the system the housing comprises other componentsthat may be arranged in many different configurations in which at leastsome of them may be located within the housing. In these embodiments theother components of the system are: v) an Analog Front End (AFE) thattransmits and receives ultrasound signals by means of electroniccomponents; vi) a processor containing software; vii) a user interfacecomprising a display screen and means to accept user's instructions; andviii) at least one memory device to store data and images processed bythe software in the processor. In these embodiments the other componentsthat are not located within the housing are located at a location nearthe patient but separated from the housing. In these embodiments theother components that are not located within the housing are incommunication with components located within, or associated with thehousing.

In some embodiments of the system the electronic components of the AFEcomprise transmitters, receivers, amplifiers, and analog to digital (A/Dand digital to analog (D/A) converters.

In some embodiments of the system the software is configured to operatethe system and to receive and process ultrasound signals received fromthe AFE to produce ultrasound images and to receive and process inertialmeasurement signals received from the IMU.

In some embodiments of the system the AFE, IMU, processor, memorydevices, and communication components can be provided as separateintegrated circuits (ICs) or integrated into one or more ASICs thatcomprise at least some of the ICs.

Some embodiments of the system comprise additional components. Theadditional components comprise at least one of: ix) a remote terminal;x) at least one additional IMU; xi) at least one magnetometer; xii) atleast one pressure sensor; and xiii) a speaker and a microphone forcommunicating with a remote health care provider. The magnetometer canbe a one-, two- or three-axis magnetometer.

In some embodiments of the system all of the other components v)-viii)are contained within a remote terminal, which is connected to thescanner via a wired or wireless communication link. In other embodimentsof the system some of the other components v)—viii) are contained withinthe scanner and the remainder located at a remote terminal, which isconnected to the scanner via a wired or wireless communication link.

In some embodiments of the system the remote terminal is a portablecommunication device. In some embodiments of the system the portablecommunication device is a smartphone. In some embodiments of the systemthe portable communication device comprises the display, the IMU, andthe processor. In some embodiments of the system the portablecommunication device fits into a socket in the housing of the scanner.In some embodiments of the system the portable communication device isan integral part of the housing. In some embodiments of the system theportable communication device is not an integral part of the housing,but is fit into the socket in the housing before performing a scan,moved together with the housing during an ultrasound scan, and ifdesired, later detached for other uses. In some embodiments of thesystem the portable communication device is connected via a cable orwireless connection to the housing and only the housing is moved.

Illustrative examples of suitable wired communication links include USB,lightning, and fiber optic, but, of course, any additional wiredcommunication is possible. Illustrative examples of wirelesscommunication links include, but are not limited to, Wi-Fi, UWB,Bluetooth, and IR.

The portable communication device can be any of many suitable devices,for example, a mobile phone, tablet, laptop. Moreover, the housing or adevice connected therewith, may be in communication with apparatuslocated in the cloud, adapted to receive data generated by, or inassociation with, the housing.

In some embodiments of the system different combinations of one or moreIMUs, processing devices and software, memory devices, power sources,and components of the AFE are located either within the housing or inthe smartphone. Some embodiments of the system comprise at least one IMUin the smartphone and at least one IMU in the housing.

In some embodiments of the system the processor is configured to receivedata collected by all sensors.

In some embodiments of the system the software is configured to executeat least one of the following: to produce ultrasound images; to analyzethe data; to decide which images are of sufficient quality to bedisplayed on the display screen; to discard low quality images; toinstruct the operator to hold the housing of the scanner in apredetermined manner; to compute the location and attitude of thescanner; to determine if the scanner is being held such that enoughpressure is being exerted on the skin to produce an image of sufficientquality; and to effectively provide instructions how to move the scannercorrectly in order to obtain satisfactory.

In some embodiments of the system instructions to the operator that aregenerated by the software are provided visually on the display screen oraudibly from the speakers. In some embodiments of the systeminstructions to the operator are provided visually on the display screenor audibly from the speakers by a trained health care professionallocated at a remote terminal.

In some embodiments of the system the task of computing the navigation,including the scanner's location, orientation, and time derivatives ofthem, is carried out by an Inertial Navigation System (INS) comprising aset of three-axis gyroscopes and three-axis accelerometers in the IMUand other sensors; the processor; and software, which is configured totake initial conditions and calibration data and the output from the IMUand other sensors to compute the Navigation, wherein the other sensorscan be at least one of a three-axis magnetometer, a pressure sensor, anda camera.

Some embodiments of the system are configured to generate accurate scansof ultrasound signals on the skin and to ensure good value images fordiagnostic purposes by using a combination of a pressure sensor and IMUand selecting only images that meet optimal values of the speed ofscanning and pressure of the scanner against the skin.

In some embodiments of the system the INS provides the following typesof data:

-   -   a. angles of orientation;    -   b. speed of the scanner; and    -   c. location of the ultrasound probe head relative to the body's        anatomy.

In some embodiments of the system the speed of the scan is calculatedfrom the angular velocity assuming motion perpendicular to the surfaceof the body.

In some embodiments of the system, for prenatal exams, the body ismodeled as a sphere, whose radius can be approximated by one or more ofthe patient's BMI, the stage of the pregnancy, or a visual estimate,e.g. in the range of 20 cm up to 70 cm for obese patients.

In some embodiments of the system typical distances for the scans are inthe range of several millimeters up to several tens of centimeters. Insome embodiments of the system the speed of the scan is between 1 mm persecond and several centimeters per second.

In some embodiments of the system the 3-axis gyroscopes and 3-axisaccelerometers of the IMU are calibrated by the manufacturer for offset,scale-factor, cross-axis sensitivity and initial orientation; and MEMSIMUs are calibrated by the user before each scan. In some embodiments ofthe system, if the motion of the scan is slow and the operator maintainsthe orientation of the scanner relative to the body being scanned withina several degrees of a predetermined starting orientation, then aone-step calibration, in which only the offset of the gyroscopes isestimated, is required, wherein the one-step calibration processcomprises holding the IMU still for several minutes and recording theoutput of the sensors; wherein the average output of the gyroscopes istaken to be their offset and the variance of each sensor is taken to beits noise.

In some embodiments of the system the operator performs a seven-phasecalibration process, wherein the seven phases of the calibration processin a coordinate system wherein the positive Z-axis points up, thepositive Y-axis points towards the right, and the positive X-axis pointsforward are:

-   -   a. Phase 1: hold the scanner still for T seconds;    -   b. Phase 2: rotate the scanner around the Y axis such that the        rotation is completed, and the scanner is stationary in the new        orientation, within T seconds;    -   c. Phase 3: hold the scanner still for T seconds, then rotate        back;    -   d. Phase 4: rotate the scanner over around X axis within T        seconds;    -   e. Phase 5: hold the scanner still for T seconds, then rotate        back;    -   f. Phase 6: rotate the scanner over around Z axis within T        seconds; and    -   g. Phase 7: hold the scanner still for T seconds, then rotate        back.

In some embodiments of the system, if the processor determines, during ascan, that not enough pressure is being exerted on the skin, aninstruction to increase the pressure is issued to the operator eithervisually on the display screen, e.g. by displaying a downward pointingarrow, and/or audibly from the speakers. In these embodiments theprocessor can determine that not enough pressure is being exerted on theskin by at least one of:

-   -   a. analyzing the image and determining that the picture is flat;        and    -   b. measuring the variance of the brightness of the image over        some region of interest in the image and determining that the        variance is smaller than a threshold value.

In some embodiments of the system the processor contains softwareconfigured to determine if an insufficient quantity of water-based gelis interposed between the ultrasound probe head and the skin and toissue an alert to the operator either visually on the display screenand/or audibly from the speakers. In these embodiments the software candetermine if an insufficient quantity of water based gel is interposedbetween the ultrasound probe head and the skin by determining if thereis weakening of the signals returning to the probe or weakening of theresulting ultrasound image.

In some embodiments of the system the processor and software of thesystem are configured to issue the following set of instructions toguide an operator to perform a scan:

-   -   a. instruct the operator to carry out a calibration procedure if        necessary by guiding the operator through the procedure;    -   b. instruct the operator to measure the patient's blood        pressure, using a blood pressure meter;    -   c. instruct the operator how to position the patient to take the        scan;    -   d. instruct the operator to position the scanner at a location        that will serve as the center of a patient coordinate system;    -   e. instruct the patient to operator the scanner with the screen        facing the patient;    -   f. provide the operator with instructions including the        direction in which to move the scanner over the surface of the        patient's body, how far to move in each direction, the speed        with which the scanner should be moved, and the amount of force        they should exert to press the scanner against the body;    -   g. advise the operator that the session is over when enough        images of sufficient quality have been collected; and    -   h. if not done so automatically, advise the operator to forward        the images to a health care professional to be interpreted.

In a second aspect the invention encompasses a method for allowing aoperator not trained for ultrasound scanning to obtain and processultrasound images of internal body organs. The method comprises:

-   -   a. providing a system comprised of a scanner and at least one        inertial measurement unit (IMU); wherein, the scanner is the        component of the system that is moved by an operator over the        surface of a patient's body to obtain the ultrasound images, the        at least one IMU is located within the scanner, and the system        is configured to issue instructions to the operator of the        system that allow scans to be performed;    -   b. follow the instructions issued by the system.

In an embodiment of the method of the second aspect, the system is thesystem of the first aspect of the invention.

In an embodiment of the method of the second aspect, the instructionsissued by the system are the instructions issued by the processor andsoftware of the system of the first aspect of the invention.

In a third aspect the invention encompasses a method for acquiringultrasound images of internal body organs. The method comprisesproviding a scanner and at least one inertial measurement unit (IMU)associated therewith, and instructions for an untrained user to operatesaid scanner.

Some embodiments of the third aspect of the method comprise issuinginstructions to the operator of the system that allow scans to beperformed also by persons not trained for ultrasound scanning includingthe patient themselves. Some embodiments of the method of the thirdaspect comprise transmitting acquired ultrasound images to a remotelocation for analysis by a healthcare professional. Some embodiments ofthe method of the third aspect comprise providing circuitry adapted toperform two-way communication between the user and a remote individualor non-monitored system. In some embodiments of the third aspect of themethod the non-monitored system comprises automated, image analysiscircuitry and the output of an automated analysis is provided to theuser and/or to a healthcare professional. In some embodiments of thethird aspect of the method the two-way communication is selected fromaudio, visual, and video communication, and combinations thereof.

In some embodiments of the third aspect of the method the scans areperformed by untrained operators and the system enables two way videocommunications between the operator and a health care professional. Insome embodiments of the third aspect of the method the output of thesystem is sent directly to a remote healthcare and/or to a non-monitoredsystem professional in real time, or shortly after images are acquired.

In some embodiments of the third aspect of the method the system enablesoverlaying an image of the scanner on top of the ultrasound scans to aida healthcare professional in interpreting the images.

In some embodiments of the third aspect of the method compriseperforming a calibration process consisting of seven phases, in acoordinate system wherein the positive Z-axis points up, the positiveY-axis points towards the right, and the positive X-axis points forward,which are:

-   -   a. Phase 1: hold the scanner still for T seconds;    -   b. Phase 2: rotate the scanner around the Y axis such that. the        rotation is completed, and the scanner is stationary in the new        orientation, within T seconds;    -   c. Phase 3: hold the scanner still for T seconds, then rotate        back;    -   d. Phase 4: rotate the scanner over around X axis within T        seconds;    -   e. Phase 5: hold the scanner still for T seconds, then rotate        back;    -   f. Phase 6: rotate the scanner over around Z axis within T        seconds; and    -   g. Phase 7: hold the scanner still for T seconds, then rotate        back.

In some embodiments of the third aspect of the method, if the processordetermines, during a scan, that not enough pressure is being exerted onthe skin, an instruction to increase the pressure is issued to theoperator either visually on the display screen, e.g. by displaying adownward pointing arrow, and/or audibly from the speakers. In theseembodiments, determining whether the not enough pressure is beingexerted on the skin can be by at least one of:

-   -   a. analyzing the image and determining that the picture is flat;        and    -   b. measuring the variance of the brightness of the image over        some region of interest in the image and determining that the        variance is smaller than a threshold value.

Some embodiments of the third aspect of the method comprise determiningthrough software analysis if an insufficient quantity of water-based gelis interposed between the ultrasound probe head and the skin and issuingan alert to the operator either visually on the display screen and/oraudibly from the speakers if an insufficiency of gel is found. In theseembodiments of the third aspect of the method, the software candetermine if an insufficient quantity of water based gel is interposedbetween the ultrasound probe head and the skin by determining if thereis weakening of the signals returning to the probe or weakening of theresulting ultrasound image.

Embodiments of the third aspect of the method comprise guiding anoperator to perform a scan by issuing the following set of instructions:

-   -   a. instructing the operator to carry out a calibration procedure        if necessary by guiding the operator through the procedure;    -   b. instructing the operator to measure the patient's blood        pressure, using a blood pressure meter;    -   c. instructing the operator how to position the patient to take        the scan;    -   d. instructing the operator to position the scanner at a        location that will serve as the center of a patient coordinate        system;    -   e. instructing the operator to position the scanner with the        screen facing the patient;    -   f. providing the operator with instructions including the        direction in which to move the scanner over the surface of the        patient's body, how far to move in each direction, the speed        with which the scanner should be moved, and the amount of force        they should exert to press the scanner against the body;    -   g. advising the operator that the session is over when enough        images of sufficient quality have been collected; and    -   h. if not done so automatically, advising the operator to        forward the images to a health care professional to be        interpreted.

All the above and other characteristics and advantages of the inventionwill be further understood through the following illustrative andnon-limitative description of embodiments thereof, with reference to theappended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows four columns each containing plots of data relating to thecalibration process;

FIG. 2 shows the results of estimating the orientation of the scanner byapplying an Extended Kalman Filter to the calibrated gyroscope and theaccelerometer data;

FIG. 3 repeats a test similar to the one shown in FIG. 2 , but themeasurements are fed into the EKF without calibration;

FIG. 4 shows the angular velocity with which the scan is being carriedout, and the tangential velocity that is derived from the angularvelocity;

FIG. 5 schematically shows an embodiment in which a smartphonecomprising components of the system fits into a socket in the housing ofthe scanner of the system;

FIG. 6 schematically shows a typical scene on the screen of a smartphoneduring a scan with the embodiment of the system shown in FIG. 5 ;

FIGS. 7A-7C are screenshots showing the effect on the images ofinsufficient coupling between the ultrasound probe head and thepatient's body;

FIG. 8 is a screen shot showing the results of a blood pressuremeasurement overlaid on the scan;

FIG. 9 illustrates movements of a scanner relative to the patient'sbody; and

FIG. 10 is a flow chart of a coupling alert process.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Herein the invention will be described in detail as a system and methodthat allow a patient to perform ultrasound scans by themselves. While adetailed example for ob-gyn is provided, a person skilled in the art caneasily adapt it to other conditions and other organs, for example,cardiovascular, lungs, kidney, thyroid, liver, prostate, bladder, andfor other sensors. Moreover, although conceived as a system for self—useby a person in a home environment, because of its portable nature, thesystem can also be effectively employed by persons not fully trained forultrasound scanning, for example by a family member, in ambulances, orin the field by an untrained soldier. Needless to say that trainedpersons may also derive benefits from using the invention as a firstapproximation, before operating other, more sophisticated equipmentavailable to them.

The other sensors referred to above can include any type of sensor thatgenerates data that is useful in improving and/or add relevantinformation to that acquired through ultrasound images. For instance,blood pressure (the importance of which in the context of the inventionwill be further discussed below) can be transmitted to the device of theinvention where it can be coupled or overlayed to other information, orcan be used to alert the user and/or a health practitioner of anypotential problems. Another example is a proximity sensor, which can beused to alert the user if not enough pressure is applied with thehousing to the body, which may result in defective readings.

An additional example of a sensor useful in the context of the inventionis an image acquisition element, which can be used, independently of IMUcomponents, to alert the user of coupling problems (e.g., due toinsufficient pressure of the device against the body or insufficientgel), or if the user is scanning too fast to generate a good qualityimage. The abovementioned and other situations that require alerting theuser are detected via image processing, which can be performed locallyin the housing or remotely by a connected device.

The scans can be performed by the patient themselves and thentransmitted to a remote location for analysis by a health careprofessional or a non-monitored system, which comprises automated, imageanalysis circuitry. Some embodiments of the system are configured toallow the use of two-way video communication, i.e. Telemedicine,enabling the patient and a sonographer or to see each other while thepatient is carrying out the scanning procedure.

The invention also encompasses a system for obtaining and processingultrasound images of internal body organs. The system is comprised ofmany components that be arranged in many different configurations,examples of which will be described herein. The component of the systemthat is essential to all configurations is called herein a “scanner,”which comprises components of the system that are moved by an operatorover the surface of a patient's body to acquire the ultrasound images.FIG. 9 illustrates the possible forms of movement of the scannerrelative to the patient's body. The scanner comprises a housing that isergonomically designed to be held by an operator and to be moved acrossthe skin of a person or animal. The housing comprises at least theminimum number of components of the system that must be located on thepatient's body to obtain the ultrasound images. These elements can beintegral with the housing or associated therewith. In the context ofthis description, the term “associated with” should be interpreted asmeaning that the elements or components to which it is referred must notnecessarily be integral with the housing, but must be in usefulcooperation therewith, For instance, where an accelerometer isdiscussed, it must move together with the housing, and when acommunication component is discussed, it must be in communication withany other component located within the housing with which it mustexchange data, or from which it must receive data. These components are:i) an ultrasound probe head, i.e. an array of ultrasound elements; ii)electronic components for wired or wireless communication with remoteterminals, and iii) a power source, e.g. a battery when the system iswireless or power supply in case of wired system; and in mostembodiments iv) at least one Inertial Measurement Unit (IMU) comprisingthe inertial sensors, i.e. a three-axis accelerometer and a three-axisgyroscope, and possibly other sensors, e.g. a three-axis magnetometerand a pressure sensor.

However, in some embodiments of the invention the inertial sensors arenot integral with the housing. Instead, the inertial sensors of thesmartphone or the like portable device (that will be discussed later)can be used, or add-on inertial sensors can be connected to the housingprior to use. In another embodiment of the invention, the housing can bea “docking housing,” i.e., a housing that only comprises componentsessential for connecting functional components such as sensors ofvarious types thereto, and said sensors can be connected to the dockinghousing as needed. This embodiment allows selecting appropriate kinds ofsensors for a given use, which can be added as “plug and play”components to the housing.

Other typical components of the system are: v) an Analog Front End (AFE)that transmits and receives ultrasound signals by means of electroniccomponents including, inter alia, transmitters (pulsers), receivers,amplifiers, and analog to digital (A/D and digital to analog (D/A)converters; vi) a processor containing software configured to operatethe system and to receive and process ultrasound signals received fromthe AFE to produce ultrasound images and to receive and process inertialmeasurement signals received from the IMU; vii) a user interfacecomprising a display screen and means to accept user's instructions,e.g. a keyboard or touch screen; and viii) a memory device or devices tostore data and images processed by the software in the processor. Indifferent embodiments some or all of these components may be locatedwithin the housing of the scanner or at a location near the patient butseparated from the housing. There are many options for arranging thesecomponents, which will be easily appreciated by the skilled person.

The electronic components, i.e. the AFE, IMU, processor, memory devices,and communication components can be provided as separate integratedcircuits (ICs) or integrated into one more ASICs that comprise all orsome of the ICs.

Optional components of the system include: ix) a remote terminal e.g. asmartphone, tablet, PC, or similar communication and computing devicethat is located near the operator or far from the operator, e.g. in aclinic or doctor's office; x) one or more additional IMUs; x) at leastone magnetometer; xi) at least one pressure sensor; and xi) a speakerand microphone for communicating with a remote health care provider.

In some embodiments of the system all the components v)—viii) arecontained within (or on in the case of the display) the housing of thescanner.

In some embodiments of the system all the components v)—viii) arecontained within a remote terminal, which is connected to the scannervia a wired or wireless communication link; wherein the wireless linkcan be formed using any known technology, e.g. Cellular, WIFI orBluetooth.

In some embodiments of the system some of the components v)—viii), e.g.some or all of the components of the AFE, are contained within thescanner and the remainder in the remote terminal, which is connected tothe scanner via a wired or wireless communication link.

FIG. 5 schematically shows an embodiment in which the display 10, an IMU12, and the processor 14 are contained in a smartphone 16, which fitsinto a socket 18 in the housing 20 that contains the other components ofthe scanner. The smartphone 16 is not necessarily an integral part ofthe housing 20 but may be fit into the socket 18 before performing ascan, moved as an integral part of the housing 20 during an ultrasoundscan, and later detached for other uses. The smartphone 16 iselectrically connected to the housing 20 by a connector 22 in the socket18, which fits into a standard port on the smartphone 16. Seen in FIG. 5is ultrasound probe head 24 at the bottom of housing 20. The term“smartphone,” as used herein, refers to any portable communicationdevice for which a fitting seat can be created in a housing such ashousing 20 of FIG. 5 , and is not intended to limit the invention to anyparticular type of communication device, existing or to be developed.The smartphone was chosen in this example, to illustrate the inventiononly, since it is a widespread device available to most people.

In another embodiment the smartphone is connected via a cable or awireless connection to the housing and only the housing or the probeitself is moved, i.e., the smartphone does not necessarily have to movein unison with the ultrasound probe.

In other embodiments, different combinations of one or more IMUs,processing devices and software, memory devices, power sources, andcomponents of the AFE are located either within the housing or in thesmartphone.

Because the IMU is, on the one hand, very noisy and, on the other hand,relatively inexpensive, in some embodiments it is advantageous to useseveral of them in one scanner, e.g. one IMU in the smartphone andanother in the housing or two or more IMUs in the housing. This willincrease the accuracy of the positioning and motion measurements andimprove the signal-to-noise (S/N) ration of the received ultrasoundsignals.

The processor is configured to receive data collected by all sensors andcontains software that is configured, inter alia, to produce ultrasoundimages; to analyze the data; and in some embodiments, to decide whichimages are of sufficient quality to be displayed on the display screen;to compute the location and attitude of the scanner, to discard lowquality images; to instruct the operator to hold the housing of thescanner in a predetermined manner, e.g. such that the display screen (ora designated symbol on the housing surface in embodiments in which thedisplay is remotely located) always faces her/him; to determine if thescanner is being held such that enough pressure is being exerted on theskin to produce an image of sufficient quality; and to effectivelyprovide instructions how to move the scanner correctly in order toobtain satisfactory images by means of an intuitive graphical cuepresented on the display screen. In other embodiments the instructionsto the operator are provided visually or audibly on the display screenand speakers or by a trained health care professional located at aremote terminal.

FIG. 6 schematically shows a typical scene on the screen of a smartphone16 during a scan with the embodiment of the system shown in FIG. 5 . Theblank area 26 on the screen is reserved, in this illustrativeembodiment, for instructions to the user from the system. Typicalinstructions include, for example: The screen is not facing you—pleasekeep it perpendicular to your body;

-   -   The image is not clear—please apply more pressure or add more        gel;    -   You're moving too fast—please slow down; and    -   Please move the housing to the right.

The task of computing the scanner's location, orientation, and timederivatives of them is carried out by an Inertial Navigation System(INS). The INS is comprised of the IMU, i.e. a set of three-axisgyroscopes and three-axis accelerometers and other sensors, e.g. usuallya three-axis magnetometer and a pressure sensor; the processor; andsoftware configured to take initial conditions and calibration data andthe output from the IMU and other sensors to compute the Navigation.

It is also possible to use other sensors in addition to the IMU,magnetometer, and pressure sensor in order to improve accuracy. Forexample, in a mobile phone there is a front camera that points towardsthe user and a rear camera that points towards objects in the room. Forthe embodiment in which a smartphone, which fits into a socket in thehousing that contains the other components of the scanner, at thebeginning of the scan the rear camera points towards a particular objectin the room. During the scan the rear camera moves with the housing andthe movement relative to the object in the image can be tracked using anoptical flow method, thereby providing another piece of information tothe navigation algorithm that can be used to correct errors.

In embodiments of the invention, the system can be configured togenerate accurate scans of ultrasound signals on the skin and to ensuregood value images for diagnostic purposes by using a combination of apressure sensor and IMU and selecting only images that meet optimalvalues of the speed of scanning and pressure of the scanner against theskin.

These sensors of the inertial measurement unit (IMU) or inertialnavigation system (INS) can be implemented using a single chip ASIC thatcontains all or some of them or as discrete chip that implements eachsensor separately or as combinations of sensors.

The IMU provides several types of data:

-   -   1. Angles of orientation, which are used to:        -   a) Provide the user with instructions how to hold the            scanner in order to get the best images,        -   b) Provide a physician or other professional with the            continuous orientation of the probe at the time a scan was            taken in order to facilitate interpretation of the image.            This information can be presented as an overlay on the            ultrasound image.    -   2. Speed of the scanner, which is used to:        -   a) Provide the user with instructions how to move the            scanner in order to get the best images. This information            can be provided to a remotely located physician so they may            be aware of how the scan is performed with all the alerts            that the operator experienced.        -   b) Filter out images that are unlikely to contain useful            information. For example, criteria for deleting images could            be speed greater than 10 cm/sec, or could also be    -   1 cm/second in a situation where slow scanning is required in        order to detect a specific phenomenon—for example, self-scanning        of the inferior vena cava (IVC) in the case of congestive heart        failure (CHF) patients.    -   3. Location of the ultrasound probe head relative to the body's        anatomy, which is used to:        -   a) provide the user with instructions how to scan the whole            area of interest in order to fully cover the organ of            interest;        -   b) provide a physician or other professional with the            scanner's continuous orientation at the time a scan was            taken in order to facilitate interpretation of the image.

The IMU, like other devices, is not perfect. IMU errors, uponintegration, form drift, an error that increases over time, andtherefore, the error of the computed location and orientation quicklypropagates over time. An example can best illustrate the problem. Assumethat due to measurement noise and other imperfections, the orientationof the device is known with an error of one milli-radian. This error isconsidered very small given the quality of, for example, a typicalsmartphone's IMU. Given this error, the processor misinterprets theaccelerometer readings, and interprets the projection of the gravitationas a horizontal acceleration of approximately one cm/sec². This smallacceleration error results in a location error of 18 meters over oneminute, clearly well beyond the acceptable error. Thus, the processormust have some additional information, and must assume some restrictionsin order to provide meaningful navigation.

The IMU installed in smartphones is based on Micro Electro-MechanicalSystems (MEMS) technology. MEMS technology provides tiny, efficient,affordable sensors, but suffers from inherent imperfections resulting inmeasurement errors. The errors can be divided into biases and noise.Formally, the only difference is that a bias varies slowly whereas noisevaries quickly. However, over the time period relevant to ultrasoundscans, and for illustrating the problem, biases can be regarded asconstant, and noise can be regarded as absolutely random.

Thus, due to biases, the IMU of a motionless device still producesmeasurements as if the device is rotating and accelerating. In order tocalibrate the IMU and find the biases a calibration procedure must bepresented. Still, due to noise, no calibration is perfect, and someresidual bias always remains. Also, noise, albeit random, only sums upto zero after an infinite number of measurements. In practice theexpected value of the noise is the square root of the number ofmeasurements times the standard deviation of the noise.

As said, the IMUs installed in smartphones are all MEMS based, subjectto strict limits of cost, size and energy consumption, and therefore,are very similar to each other. Their noise and bias figures are inprinciple the same.

As a result of biases and noise, and given the quality of MEMS IMUS, thenavigation process must integrate more measurements, and utilize someprior assumptions, in order to mitigate the IMU errors. When scanningwith the scanner, the distances moved are small and the scanning speedis relatively slow, which frequently results in the noise generated inthe IMU being larger than the signal. Typical distances for these scansare in the range of several millimeters and up to several tens ofcentimeters and typical speeds of 1 mm/sec to several centimeters persecond. Thus, successful navigation relies on optimal calibrationallowed by the system, the mission, and the user, and on the integrationof other available cues.

Some bias errors are calibrated for at the manufacturing level. However,some biases vary over time and must be calibrated prior to use. In thecase of the scanner described herein, the calibration process is limitedto simple steps that the user can easily perform. A prior assumptionthat can be made is that the user cooperates by holding the scanner suchthat she/he faces the display on a horizontal table.

If the scanner is placed on a horizontal surface, the acceleration axisshould be equal to 9.81 downward, so if a different value than 9.81 ismeasured, the processor can calibrate the offset and add the offset toeach measurement. If the user is required to calibrate the IMU, then,after the system is activated before the beginning of a scanningsession, the user is prompted, either by the software in the processoror by a remotely located technician, how to calibrate the gyroscopes andaccelerometers. IMU's, especially those made by MEMS technology, must becalibrated before every use as the calibration values vary from day today and each time they are turned on.

A calibration procedure comprising seven phases will now be described.This procedure is one of many that can be used with the scanner and isonly meant to illustrate the principles involved. The inventors haveused other calibration procedures comprising fewer than seven phases andanticipate that other procedures involving, for example a differentorder of the phases or more or less than seven phases, can be devisedand used, and the selection of the actual calibration method is notessential as long as it yields the required calibration result. In manysituations, especially when only slow motion is allowed and the userkeeps the screen toward her within several degrees, a one-stepcalibration, in which only the offset of the gyroscopes is estimated,provides excellent results. In this protocol, the IMU is held still forsome time, and the output of the sensors is recorded. The average outputof the gyroscopes is taken to be their offset, and the variance of eachsensor is taken to be its noise. The Earth rotation, approximately 15degrees per hour, is usually negligible compared to the gyroscopesoffset.

For this example, a coordinate system is selected. In this coordinatesystem the positive Z-axis points up, the positive Y-axis points towardsthe right, and the positive X-axis points forward. The letter T is usedfor the duration of the calibration, it can be, for example, 1, 3, 5, or10 seconds or longer pending on the type of the IMU. The value of T is acompromise between the degree of accuracy and the patience of the user.The procedure has the following seven phases:

-   -   Phase 1: Hold the scanner still for T seconds.    -   Phase 2: Rotate the scanner around the Y axis such that the        rotation is completed and the scanner is stationary in the new        orientation, within T seconds    -   Phase 3: Hold the scanner still for T seconds, then rotate back.    -   Phase 4: Rotate the scanner over around X axis within T seconds.    -   Phase 5: Hold the scanner still for T seconds, then rotate back.    -   Phase 6: Rotate the scanner over around Z axis within T seconds.    -   Phase 7: Hold the scanner still for T seconds, then rotate back.

The data from the three accelerometers and three gyroscopes arecollected by the electronics and transferred to the processor duringthese seven phases. An example of gyroscopes data is shown in FIG. 1 .

FIG. 1 shows four columns each containing plots of data relating to thecalibration process. In each column, the three rows refer to the threegyroscopes: x, y and z. In each plot of FIG. 1 , the horizontal axis isthe time of measurement and the vertical axis is the measurement takenfrom the gyroscopes or the error of this measurement. Vertical linesmark borders between the seven phases, wherein phases are labeled asfollows: the 1^(st) S0, the 2^(nd) RY, the 3^(rd) SY, the 4^(th) RX, the5_(th)SX, the 6^(th) RZ, and the 7^(th) SZ. The first letter, either Sor R, refers to either “stationary” or “rotating” situation. The secondletter, either X, Y or Z, refers to the axis around which the rotationis taken or the axis around which a rotation was taken prior to thestationary situation.

Referring to FIG. 1 , one can see how the data is interpreted. Theleftmost column contains the data collected from the gyroscopes. At thefirst phase, S0, at time 0-5 seconds, the device is stationary and thegyroscopes output their offset and any constant rotation, e.g., theEarth rotation. At the second phase, RY, at time 5 to 10 seconds, thefirst 2.5 seconds shows a 180 degrees rotation around the y-axis. Thus,y-gyro shows a large signal. And so on for the other phases.

The next column, the second from the left, shows the error of themeasurements. Note that in this case the error is known since everygyroscope senses either zero rotation, or a known angular velocity of180 degrees over 2.5 seconds period, or approximately 1.26 rad/sec. Inthis column one can see three features of the signal. The offset isbetter seen, there is signal at time of rotation on axes other than theaxis of rotation, and the output of the rotating gyro is different thanexpected. The latter two phenomena result from cross-axis measurementand scale factor errors.

The first phase, S0, in this example between 0 and 10 seconds, isstationary, and therefore, apart from a small contribution of therotation of the Earth, should produce zero. However, it can be seenthat, in this example, the measurements are offset at approximately[0.12, −0.18, 0.02] rad/sec including less than 10⁻⁴ rad/sec for therotation of the Earth. At the third phase, SY, data are taken from thesame sensors after the sensor was rotated 180 degrees around y-axis, andin this case the contribution of the rotation of the Earth for axis xand z are inversed. Thus, averaging the data at S0 and SY gives anestimate for the offset of the x- and y-gyro. Similar protocol appliesto the other axes using other rotations.

The next column, the third from the left, shows the same data as in theprevious two columns after the computed offset is removed. Accordingly,stationary states now show 0 rad/sec plus some noise.

Inspecting the third column one can compute the cross-axis effect. Forexample, the output of the x-gyro during RY phase should have been zero,and is actually approximately 0.013 rad/sec. The ratio between theaverage output of the x-gyro, approximately 0.013 rad/sec, and theaverage output of the y-gyro, approximately 0.126 rad/sec produces thecross-axis effect between y and x axes, which is approximately 0.01.Similarly, one can work out the relations for all nine cross-axispossibilities.

The scale factor can also be computed from the data in this column bycomparing the error to the expected result. For example, an error of0.125 rad/sec is seen at the second row at phase RY. This error isapproximately 0.1 of the signal, and therefore, the scale factor is 1.1.

The scale factor and the cross-axis can be combined into a matrix.Multiplying the original results by the inverse of this matrix andsubtracting the original data produces the results on the last column,which only contains noise. This noise is conveniently used to estimatethe detector noise required by the Extended Kalman Filter.

Note that time-constant angular velocity, as shown here, is only for theclarity of the example. Replacing every computation by its average overthe duration of the phase produces the same results.

The algorithm used by the software in the processor for calibrating thegyroscopes' offsets is:

-   -   1. O_s0=mean of the data collected at phase 1 for each of three        gyroscopes.    -   2. O_sy=mean of the data collected at phase 3 for each of three        gyroscopes.    -   3. O_sz=mean of the data collected at phase 7 for each of three        gyroscopes.    -   4. Compute:

Offset for x-axis=B _(x) ^(ω)=(O_s0_(x) +O_sy _(x))/2  a)

b)Offset for y-axis=B _(y) ^(ω)=(O_s0_(y) +O_sy _(y))/2  a)

Offset for z-axis=B _(z) ^(ω)=(O_s0_(z) +O_sy _(z))/2  c)

-   -   -   Wherein, the subscripts x, y, z refer respectively to the            data from the x, y, and z gyroscopes.

The algorithm used by the software in the processor for calibrating thegyroscopes' scale factors is:

-   -   5. O_ry=mean of the data collected at phase 2 for each of three        gyroscopes.    -   6. O_rx=mean of the data collected at phase 4 for each of three        gyroscopes.    -   7. O_rz=mean of the data collected at phase 6 for each of three        gyroscopes.    -   8. Compute:

Scale factor for x-axis=(O_rx _(x) +B _(x) ^(ω))*T/pi  a)

Scale factor for x-axis=(O_rx _(y) +B _(y) ^(ω))*T/pi  b)

Scale factor for x-axis=(O_rx _(z) +B _(z) ^(ω))*T/pi  c)

The algorithm used by the software in the processor for calibrating thegyroscopes' cross-axis sensitivity is based on the matrix C′″

-   -   9. where:

C _(x,x) ^(ω)=(O_rx _(x) −B _(x) ^(ω))*T/Pi  a)

C _(x,y) ^(ω)=(O_rx _(y) −B _(x) ^(ω))*T/Pi  b)

C _(x,z) ^(ω)=(O_rx _(z) −B _(x) ^(ω))*T/Pi  c)

C _(y,x) ^(ω)=(O_rx _(x) −B _(y) ^(ω))*T/Pi  d)

C _(y,y) ^(ω)=(O_rx _(y) −B _(y) ^(ω))*T/Pi  e)

C _(y,z) ^(ω)=(O_rx _(z) −B _(y) ^(ω))*T/Pi  f)

C _(z,x) ^(ω)=(O_rx _(x) −B _(z) ^(ω))*T/Pi  g)

C _(z,y) ^(ω)=(O_rx _(y) −B _(z) ^(ω))*T/Pi  h)

C _(z,z) ^(ω)=(O_rx _(z) −B _(z) ^(ω))*T/Pi  i)

The algorithm used by the software in the processor for computing thethree projections of the gravity on the three accelerometers in initialbody coordinates is:

-   -   1. A_s0=mean of the data collected at phase 1 for each of three        accelerometers.    -   2. A_sy=mean of the data collected at phase 3 for each of three        accelerometers.    -   3. A_sz=mean of the data collected at phase 5 for each of three        accelerometers.    -   4. Compute:

x-projection of gravity=A_ref_(x)=(A_s0_(x) −A_sy _(x))/2  a)

y-projection of gravity=A_ref_(y)=(A_s0_(y) −A_sy _(y))/2  b)

z-projection of gravity=A_ref_(z)=(A_s0_(z) −A_sy _(z))/2  c)

An Extended Kalman Filter (EKF) is now used to estimate the orientationof the scanner.

The state vector at time k ({circumflex over (x)}_(k)) has sevenmembers: three components of the angular velocity in body-framecoordinates ({circumflex over (ω)}_(k) ^(b)) and four components of thequaternion ({circumflex over (q)}_(k)) representing the orientation ofthe scanner or the rotation of the scanner's body-coordinates relativeto the room's assumed inertial coordinates.

${\hat{x}}_{k} = \begin{bmatrix}{\hat{\omega}}_{k}^{b} \\{\hat{q}}_{k}\end{bmatrix}$

The transition function, predicting the next step state vector is:

${\hat{x}}_{{k + 1},{predicted}} = \begin{bmatrix}{\hat{\omega}}_{k}^{b} \\{\frac{1}{2}{{\hat{q}}_{k} \otimes {\hat{\omega}}_{k}^{b}}{dt}}\end{bmatrix}$

where dt is the time step and is the quaternion multiplication operator.

The measurement vector is:

$Z = \begin{bmatrix}{\overset{\sim}{a}}_{k}^{b} \\{\overset{\sim}{\omega}}_{k}^{b}\end{bmatrix}$

where a_(k) ^(b) is the output of the accelerometer triad at time k,which in turn equals to:

a _(k) ^(b) =c ^(a)(ǵ ^(b) +δa _(k) ^(b))+B ^(a) +u ^(a)

here C^(a) is a 3×3 matrix whose diagonal consists of the scale factorsof the accelerometers triad, the off-diagonals components are thecross-axis sensitivity of the accelerometers, B^(a) is the biases of theaccelerometers, δa_(k) ^(b) is the specific force per unit mass applieddue to real accelerations, ǵ^(i) is gravity in body coordinates, andu^(a) is noise. As an approximation ǵ^(i) is taken from A_ref computedat the calibration process.

Similarly,

ω_(k) ^(b) =C ^(ω)({acute over (ω)}^(i))+B ^(ω) +u ^(ω))

The predicted measurement is:

${\hat{Y}}_{k + 1} = {\begin{bmatrix}{\hat{g}}^{b} \\{\hat{\omega}}_{k}^{b}\end{bmatrix} = \begin{bmatrix}{{\hat{q}}_{k} \otimes \overset{\prime}{g^{i}} \otimes {\hat{q}}_{k}} \\{\hat{\omega}}_{k}^{b}\end{bmatrix}}$

C^(a) and B^(a), as well as C^(ω) and B^(ω) are those calculated at thecalibration process.

Implicitly, this filter assumes that the specific force δa_(k) ^(b)(acceleration without gravity) is very small compared to thegravitation, and therefore the accelerometer output vector points down.This situation caps a strong limit on the rotation error thusrestraining gyroscope drift.

FIG. 2 shows the results of estimating the orientation of the scanner byapplying an Extended Kalman Filter to the calibrated gyroscope and theaccelerometer data. The left most column shows the output of thegyroscope with a dotted line, the Extended Kalman Filter (EKF)estimation of the rotation with a broken line, and the true rotationwith a solid line. Each row depicts one axis: x, y and z. The leftcolumn relates to the angular velocity as measured at body-fixedcoordinates. Looking for example at the x-gyro at the top, the truerotation is zero. The sensor produces approximately −0.18 rad/sec, whichresults from offset. The true rotation and the calibrated signal areclose together near zero. Note that for y-axis a true rotation of 0.1rad/sec is applied. All measurements enclose some noise of the order ofmagnitude of several milliradians per second. The noise is more easilyseen at the output of the z-gyro because without large offset orrotation the scale of the figure reduces to noise level. The rightmostcolumn shows the four elements of the quaternion used in the EKF toestimate the orientation. Again, solid lines and broken lines are usedfor the real and the estimated quaternion, and they fall very close toeach other. The middle column depicts the orientation in Euler angles,which are easier to interpret. Since an angular velocity of 0.1 rad/secis applied the y-angle advances at this velocity. The solid and brokenlines are so close that they cannot be distinguished. The dynamics ofthe error can better be seen on the x- and z-angles where some erroraccumulates when y-angle nears 90 degrees. Of course, 180 degrees andminus 180 degrees refer to same angle and are not an error. Theaccumulation of error when y-rotation nears 90 degrees is notaccidental, and results from numerical effect. The translation ofquaternion to Euler angles uses inverse trigonometric functions and isvery sensitive near 90 degrees.

FIG. 3 repeats similar test to the one shown in FIG. 2 , but themeasurements are fed into the EKF without calibration. One can observethe errors in the signal, the offset at the y-axis and the cross-axiseffect on the others. These errors translate into a large error in they-angle, and observable errors in the x- and z-angles.

The ultrasound scan depends on holding the scanner such that somepressure is exerted on the skin. When the pressure drops, the scannerproduces a flat image. The processor analyzes the image, and uponconcluding that the picture is flat or using similar criteria such asmeasuring the variance of the brightness of the image over some regionof interest, instead of the entire picture. If the brightness is smallerthan a threshold value, it issues an instruction to the operator toincrease pressure. In an embodiment this instruction may include, as anexample, the appearance of a down-pointing arrow on the display screenwith vocal instruction to increase pressure on the skin.

It is common to use a water-based gel in order to provide a smooth mediafor the ultrasound beams to propagate from the probe to the body,otherwise the beams will attenuated when passing through air. Using theresulting signal or image it is possible to determine whether thecoupling between the probe and the body is sufficient. This, forexample, can be determined by the weakening of the signals returning tothe probe or by the weakening of the resulting ultrasound image. FIG. 7Ais a screenshot showing good coupling between the ultrasound probe headand the patient's body and FIG. 7B and FIG. 7C show examples ofinsufficient or partial coupling. This process can be carried out in themobile device processor or in the controller of the AFE, in a componentof the device containing the ultrasound transducer, or in externalsoftware.

The speed of the scan can be calculated from the angular velocity. Theprocessor assumes motion perpendicular to the surface of the body. Forprenatal exams, the body can be modeled as a sphere, for example R₀=20,30, 40 or even 70 cm for obese patients. The radius can be betterapproximated based on the patient's BMI and stage of the pregnancy. Thespeed can be approximated as:

{circumflex over (V)} _(k)={circumflex over (ω)}_(k) ^(b) ×R _(k) ^(b)

where {circumflex over (ω)}_(k) ^(b) is the angular velocity at bodycoordinates, estimated by the filter, and R_(k) ^(b) is computed asR₀ú_(x) and ú_(x), is the unit vector pointing down from the scanner.Under normal conditions the angular velocity is dominantly along thescanner y-axis, i.e., the scanner moves right to left or left to rightalong a sphere, and the speed is approximately R₀{circumflex over(ω)}_(y) _(k) ^(b).

FIG. 4 shows the angular velocity with which the scan is being carriedout, and the spatial velocity that is derived from the angular velocity.The third column of the figure shows the three components of thevelocity in radial coordinates along the belly of a pregnant patient.The X-axis refers to radial motion from the center of the belly to theoutside. This motion is by assumption zero. The y-axis refers to motionacross the belly from bottom to top, and z-axis refer to motion fromright to left. The other columns show the same information as the treecolumns in FIG. 2 and are shown for reference. The range of permittedvelocities is a characteristic of the scanner, and is typically severalcentimeters per second. This slow motion produces radial acceleration ofas little as one millimeter per second squared, which means that theacceleration of gravity can be used by the EKF as a good approximationof the acceleration in the downward direction. Thus, when the computedvelocity is not within a permitted range, the scan is discarded and aninstruction is issued to the patient to go slower.

Combining the speed and orientation, the scanner can ensure that theuser is instructed to cover a predetermined range of angles, and to doit within the permitted velocity range. Adding the quality of the imageproduced by the image processing a proper pressure on the skin is alsomaintained. Altogether this ensures a good examination.

Since in many cases a physician or other trained healthcare professionalwill either directly observe the results of the scan or be provided withthe scans for analysis, it is important that they be provided with allof the information necessary to understand the data they are provided.In the case of prenatal scans, blood pressure is measured at everyprenatal visit. So at home, the blood pressure of the patient shouldalso be measured and the result of the measurement added to the recordof the ultrasound scans. High blood pressure in pregnancy is animportant diagnosis and indicator for preeclampsia and is very importantin determining how the rest of the pregnancy is managed prior todelivery, the timing of delivery, risk of complications, and long-termmaternal outcomes. It also affect the way that a sonographer will relateto the scans since, if the fetal heartbeats are low and the mother'sblood pressure is low it is possible that the fetus is healthy; howeverif the fetal heartbeats are low and the mother's blood pressure isnormal, this indicates that the fetus is probably sick. FIG. 8 is ascreen shot showing an embodiment of how the results of a blood pressuremeasurement can be displayed to a physician or other trained healthcareprofessional both as a written message and as an overlay on the scan.

The scanner is a “black box” as far as the operators of the scanner areconcerned. The algorithms discussed above are all useful only to theinternal working of the system, whose processor is programmed to utilizethem in order to generate instructions to the patient to guide themthrough the process of collecting ultrasound scans that are ofsufficient quality to provide useful information. The patients only haveto follow the visual or audible instructions that they receive from thecomponents of the system or from a sonographer in the case ofTelemedicine. It is also possible to show video instructions by means ofanimations.

In general, a typical set of instructions issued by the system to guidean operator to perform a scan will comprise the following:

-   -   a) instruct the patient to carry out a calibration procedure, if        necessary, by guiding the patient through the procedure e.g. the        single step or the seven stages of the calibration procedures        described herein;    -   b) instruct the patient to measure her blood pressure, using a        blood pressure meter;    -   c) instruct the patient how to position themselves to take the        scan, e.g. horizontally on their back for a pre-natal scan;    -   d) instruct the patient to position the scanner at a location        that will serve as the center of a patient coordinate system,        e.g. on the navel for a prenatal exam, between the nipples for a        heart scan, of three finger widths from the nipple on the right        or left sides for a scan of the lungs;    -   e) instruct the patient to position the scanner with the screen        facing them;    -   f) provide the patient with instructions including the direction        in which to move the scanner over the surface of their body, how        far to move in each direction, the speed with which the scanner        should be moved, and the amount of force they should exert to        press the scanner against the body;    -   g) advise the patient that the session is over when enough        images of sufficient quality have been collected; and    -   h) if not done so automatically, advise the patient to forward        the images to a health care professional to be interpreted.

In some embodiments of the invention, the output of the scanner may besent directly to a healthcare professional, e.g. the patient's personalphysician, in real time or shortly after they are acquired, and some orall of the instructions to the patient may be sent by the physician,especially if a particular region of the anatomy has to be studied ingreater depth than is normally possible from general scans. As an aid tothe physician, in some embodiments of the system, software in theprocessor is configured to overlay an image of the scanner on top of theultrasound scans. In other embodiments, the processor is configured torelay the instructions that are sent to the operator during the scan sothe physician can understand what instruction was presented and at whattime with respect to the images.

Example 1: Coupling Alert

The following exemplifies a coupling alerting procedure according to oneparticular embodiment of the invention. The procedure involves thefollowing steps:

-   -   a. Image acquisition—Construction of the ultrasound image from        the echoes received from the body organs to the transducer.    -   b. Image pre-processing—At the beginning of the process, the        frames undergo image pre-processing that normalizes the variance        between frames from different scans.    -   c. Total Black Frame (TBF) test—following the image        pre-processing the algorithm performs a TBF test. In the TBF        test, the percentage of pixels that are absolute black in the        entire current frame are examined, in order to find frames that        qualify for a TBF condition.    -   d. Coupling condition classification—The coupling condition of        any side (left/right) of each frame is made by a decision tree        classifier.    -   e. Buffer test—Each classification is saved in a buffer on        length of 16 decisions. If 80% of the decisions indicate an        insufficient coupling, the user is instructed to improve skin        contact or add more gel.    -   f. Displays an alert to the operator—While performing a scan,        the user receives real-time feedback regarding the coupling        condition. In case of 80% frames with insufficient coupling, the        user is instructed to improve skin contact or add more gel.    -   g. Add image to recording—If good coupling is detected, the        frame is recorded.    -   h. Displays an alert to the operator (TBF)—If no coupling is        identified, the system guides the user to hold the cradle        tighter to the skin.    -   i. Drop image from recording— in TBF cases the frame is not be,        thus improving the received image.    -   j. Display image on screen—all images are displayed on the        screen (TBF, insufficient coupling and good coupling).

The process is shown, in flow chart form, in FIG. 10 .

Example 2: “Scan Too Fast” Alert

The following illustrated a procedure for dealing with a user who ismoving the housing too fast to produce a good quality scan.

From the scanned image the following two steps are performed to acquirea value for the scan speed:

-   -   a. Detecting a change in a large portion of the image; and    -   b. Detecting the optical flow to obtain the speed.

The first step is aimed at distinguishing between the embryo'smovements, and the scanner's movement. The embryo's movements arelocalized and so they do not change a large portion of the image. Incontrast, a scanner movement will change all the image at once. Toestimate the change, a temporal standard deviation is calculated over 6frames. If significant change is detected in more than 0.5% of the totalscan pixels, this signifies that a movement has been made.

To evaluate an overall change in the picture, a change per second inpixel intensity is evaluated across the image. A pixel temporal standarddeviation is used as an estimator for change. For an image I(x, y, n)where “n” is the number of frames, and each frame is taken in time t(n).The following calculation is used to evaluate change:

${\sigma\left( {x,y,n} \right)} = {\frac{1}{6}\sqrt{{\overset{n}{\sum\limits_{i = {n - 5}}}{I\left( {x,y,i} \right)^{2}}} - \left( {\overset{n}{\sum\limits_{i = {n - 5}}}{I\left( {x,y,i} \right)}} \right)^{2}}}$

This yields a measurement of the amount of change per frame. To evaluatethe change in time the value is normalized by the mean FPS

${\sigma^{*}\left( {x,y,n} \right)} = {{\sigma\left( {x,y,n} \right)} \cdot \frac{6}{{\overset{n}{\sum\limits_{i = {n - 5}}}{t(n)}} - {t\left( {n - 1} \right)}}}$

In the next step the number of pixels that have change dramatically iscalculated:

${C\left( {x,y,n} \right)} = \left\{ \begin{matrix}{1;{\sigma^{*} > {Th}}} \\{0;{else}}\end{matrix} \right.$

where Th is a threshold empirically selected to distinguish betweennoise- and motion-related changes. In order to determine the requiredthreshold value, in one embodiment the mean standard deviation between10 sequential frames is calculated for 100 scans, which have been takenwith the ultrasound device of the invention. It should be taken when thedevice is held still, for instance on a pregnant women abdomen with nosignificant fetal movements. Th value are calculated as the mean andthree standard deviations of the calculated values.

Now the sum of C is calculated to understand which percent of the imagehas changed.

${{{If}\frac{\overset{X}{\sum\limits_{x = 1}}{\overset{Y}{\sum\limits_{y = 1}}{C\left( {x,y,n} \right)}}}{XY}} > 0.5},$

the frame is considered as a moving frame.

For a moving frame, an optical flow V_(x), V_(y) is calculated using theLucas-Kanade method with pyramids. Corners in the centre of the imageare used for calculation using Harris corner detector.

The optical flow gives the speed per frame. In order to attain the speedin time it should be normalized by the FPS.

$\left\lbrack {V_{x}^{*},V_{y}^{*}} \right\rbrack = \frac{\left\lbrack {V_{x},V_{y}} \right\rbrack}{{t\lbrack n\rbrack} - {t\left\lbrack {n - 1} \right\rbrack}}$

Although embodiments of the invention have been described by way ofillustration, it will be understood that the invention may be carriedout with many variations, modifications, and adaptations, withoutexceeding the scope of the claims.

1. A system for acquiring ultrasound images of internal body organs,comprising a scanner and at least one inertial measurement unit (IMU)associated therewith, wherein the system is configured to issueinstructions to the operator of the system that allow scans to beperformed also by persons not trained for ultrasound scanning includingthe patient themselves, and wherein when the scans are performed byuntrained operators, the scans are transmitted to a remote location foranalysis by a healthcare professional.
 2. The system of claim 1, whichis configured to allow two-way communication between the operator and aremote individual or non-monitored system.
 3. The system of claim 2,wherein the non-monitored system comprises automated, image analysiscircuitry.
 4. The system of claim 2, wherein the two-way communicationis selected from audio, visual, and video communication, andcombinations thereof.
 5. The system of claim 2, wherein when the scansare performed by untrained operators, two way video communication isenabled between the operator and the health care professional, enablingthem to see each other while the operator is carrying out the scanningprocedure to aid the health care professional in interpreting the imagesand to provide guidance if necessary.
 6. The system of claim 2, whereinthe system is configured such that the output of the system is sentdirectly to a remote healthcare professional and/or to a non-monitoredsystem in real time, or shortly after images are acquired.
 7. The systemof claim 1, which is configured to overlay an image of the scanner ontop of the ultrasound scans to aid a healthcare professional ininterpreting the images.
 8. The system of claim 1, comprising componentsin, or associated with the housing, including: i) an ultrasound probehead; ii) the at least one IMU, which comprises a three-axisaccelerometer and a three-axis gyroscope; iii) electronic components forwired or wireless communication with remote terminals, and iv) aninternal or external power source.
 9. The system of claim 8, furthercomprising as additional components of the system: v) an Analog FrontEnd (AFE) that transmits and receives ultrasound signals by means ofelectronic components; vi) a processor containing software; vii) a userinterface comprising a display screen and means to accept user'sinstructions; and viii) at least one memory device to store data andimages processed by the software in the processor.
 10. The system ofclaim 9, further comprising at least one of: ix) a remote terminal; x)at least one additional IMU; xi) at least one magnetometer; xii) atleast one pressure sensor; and xiii) a speaker and a microphone forcommunicating with a remote health care provider.
 11. The system ofclaim 9, wherein all of the other components v)—viii) are containedwithin a remote terminal, which is connected to the scanner via a wiredor wireless communication link.
 12. The system of claim 9, wherein someof the other components v)—viii) are contained within the scanner andthe remainder are located at a remote terminal, which is connected tothe scanner via a wired or wireless communication link.
 13. The systemof claim 12, wherein the remote terminal comprises the display, the IMU,and the processor.
 14. The system of claim 9, wherein the software isconfigured to execute at least one of the following: to produceultrasound images; to analyze the data; to decide which images are ofsufficient quality to be displayed on the display screen; to discard lowquality images; to instruct the operator to hold the housing of thescanner in a predetermined manner; to compute the location and attitudeof the scanner; to determine if the scanner is being held such thatenough pressure is being exerted on the skin to produce an image ofsufficient quality; and to effectively provide instructions how to movethe scanner correctly in order to obtain satisfactory.
 15. The system ofclaim 14, wherein instructions to the operator that are generated by thesoftware are provided visually on the display screen or audibly from thespeakers.
 16. The system of claim 14, wherein instructions to theoperator are provided visually on the display screen or audibly from thespeakers by a trained health care professional located at a remoteterminal.
 17. The system of claim 14, wherein, if the processordetermines, during a scan, that not enough pressure is being exerted onthe skin, an instruction to increase the pressure is issued to theoperator either visually on the display screen, e.g. by displaying adownward pointing arrow, and/or audibly from the speakers.
 18. Thesystem of claim 17, wherein the processor determines that not enoughpressure is being exerted on the skin by at least one of: a. analyzingthe image and determining that the picture is flat; and b. measuring thevariance of the brightness of the image over some region of interest inthe image and determining that the variance is smaller than a thresholdvalue.
 19. The system of claim 1, comprising an electronic communicationcomponent selected from one or more of USB, Lightning, fiber optic,Wi-Fi, UWB, Bluetooth and IR.
 20. The system of claim 1, comprising anIMU-independent component adapted to alert the user in case ofinsufficient coupling between the apparatus and the body or if thescanning speed is too fast.
 21. (canceled)